1. Field of the Invention
This invention relates to an improvement in a coupling for earthmoving scrapers and more particularly to a novel and improved push-pull coupling for tractor-scraper units used for excavation.
2. Description of the Prior Art
In general, the coupling for tractor-scrapers, in particular, tractor-scraper unite used for excavation comprises a push block and a pulling hook which are mounted on the tail end of a forward scraper, and a push block provided with shock absorbing means and a moveable means or bail to engage the pulling hook which are mounted on the front of a rearward scraper.
One type of prior art device employs in principle a shock absorber of the spring type, however, the shock absorber is actuated only when the rearward scraper pushes the forward scraper and cannot effectively absorb or take up the shock taking place when the forward scraper pulls the rearward scraper. Furthermore, such type of coupling of the prior art is disadvantageous in that the above-mentioned components are mounted in such a manner that the tractive power of the forward scraper is transmitted to the tractor frame of the rearward scraper being pulled, and therefore the tractor frame is liable to be deformed.